Pressure measuring devices are known, for measuring pressure under various circumstances, in the form of absolute or differential pressures. In many known pressure measuring devices of this kind, the device has a member such as a diaphragm which is deformable by the pressure to be measured. The diaphragm closes a pressure-receiving chamber which is subjected to the pressure to be measured, and tensile or compressive deformation of the diaphragm is converted into electrical signals by strain measuring strips which are arranged on suitable positions on the diaphragm, the signals being sensed by a Wheatstone bridge. As a diaphragm undergoes deformation to a different extent over its entire surface, in the prior art pressure measuring devices, the diaphragm is usually reinforced at its centre by rigid plates fixed thereon. However, the consequence of this is that the part of the diaphragm which is involved in the deformation caused by the pressure force applied thereto and which comprises the resilient annular portion remaining outside the reinforcing plates cannot be precisely defined, and also depends on the degree of diaphragm deflection, that is to say, it depends on the magnitude of the pressure to be measured. This means that the pressure measurement action of many known devices does not have the desired linear nature, quite apart from the fact that its responsiveness, measuring sensitivity and liability to be influenced by various factors such as fluctuations in temperature are often unsatisfactory.